The 3rd gen Mazda3 HID headlights perform very well and are highly rated by many reviewers out there. However, ever since buying this car, I noticed one thing: the headlights are aimed too far to the left compared to what I was used to with Z-beam and "up sweep" headlight beam patterns. There is no doubt in my mind that this was intentional from the factory in order to meet DOT regulations. In a nutshell, DOT regulations requires sufficient "hotspot" luminance to ideally light up overhead road signs but also limit upwards luminance in the upper right side of the lighting area to limit excessive driver side mirror reflective glare of other cars.

The 3rd gen HID headlights produce a Z-beam beam pattern, thus glare control is already excellent and of UNECE regulation 98 specifications (the DOT Z-beam found in the 3rd gen non-HID headlights are much shallower/less pronounced). As stated already about my observations on the factory headlighting aiming, aside from my theory that the root cause is DOT regulations, the cause is explained by the shop manual's aiming specs and what is marked on the headlight lens:
The headlights are marked "DOT VOR", meaning you aim using the right side of the beam pattern's horizontal cut off line, with zero degrees of declination. As shown in the diagram above (courtesy/copyright of Mazda), the headlights are aimed to where the flat cut off line meets the down sweep point. The result: the down sweep to the left side horizon cut off line is far to the left.

I want even better lighting performance, safely, however. The European (now UN) standard had tighter glare controls, except for driver side mirror glare of passing cars. This is no problem in many countries because aside from USA, Canada, and Australia, convex driver side mirrors are allowed and in common place. Convex mirrors have a minification factor in what's in view, thus light dazzle is greatly reduced/controlled. Flat driver side mirrors (what is only allowed here) cannot do this except for filtering or tinting. The rest of the tighter glare controls also means reduced or shifted hotspot luminosity, thus overhead road sign lighting is reduced. NHTSA in the US repeatedly state this as a disadvantage and claim that this disadvantage is a non-issue in Europe due to "prevalence of lit road signs". This is untrue as half the road signs in Europe are unlit and the European standard is in fact, still sufficient to light overhead road signs.

With that in mind, converting the headlight aiming to European aiming poses no danger and is 100% legal in Canada.

First, you must enable the ability to aim the headlights horizontally. This is capped off from the factory to meet DOT regulations as there are no provisions defined for horizontal aiming of visual optically aimed DOT headlights (this is to accommodate many plain flat cut off headlights out there, commonly found on domestics).

1. Partially pull back the fender liner. There are a couple of screws at the bottom corner of the bumper which fasten the fender liner in place as well as several plastic clips. It might be easier to do this work with the car jacked up, but it is not necessary if you turn the wheels all the way to one side and work on this one side at a time (what I did).
2. Using a flash light, look high above inside the bumper cavity and you will see the plastic caps hiding the horizontal adjusters:
3. Move the clipped on wiring harness, if necessary and using a small flat tip screwdriver, pry off the cap. The cap is on very tight! The amount of working room is very small, so care must be taken to not damage these expensive headlights! If you must, jack up the car so that you can reach into there easier and also have more room to see the cap. Fighting to get the cap off took many minutes, but persistence won the day, eventually.
4. The horizontal adjuster is now exposed. Reinstall the fender liner, then move on to the other side and do the same thing again.
5. Once you are done with the other side, reinstall the fender liner too. After this point, you no longer need to be under the car.

Now, make preparations to aim your headlights. There's 3 different ways to do this: find a wall and flat ground and do this at night, or do this inside a BIG garage (with level ground, of course), or use an optical aimer tool (usually found at car dealers of European makes).

Empty the car of all baggage/substantial weight in the trunk. Spare tire and jack needs to remain in place as you are trying to achieve close to factory weight distribution as possible.

Ensure no one is in the car and nothing of substantial weight on any seats

The amount of gas in the tank greatly affects the aim. I don't recommend aiming the headlights with less than half a tank unless you have AFS since a level sensor is used for automatic vertical adjustment

If you are using an optical aimer tool, you can skip all of the steps below and just set the tool to use 1.0% declination aim. This is the most accurate way to aim the headlights.
For most of us mortals, using flat ground, a wall, and your eye balls is the only way to do this.

1. Assuming you found your flat ground and wall, align perpendicularly and pull up to the wall as close as possible.
2. Make a mark for the center of the car on the wall, as reference.
3. Make marks on the wall indicating the center of the headlights. The center of the headlights is found by looking for a "dot" in front of the projector. It can greatly help to measure from the ground up to where the "dot" is. My car measured at 70cm, but this all varies for each different car and state of suspension! (diagram courtesy/copyright of Mazda)
4. Measure away from the wall 3 meters (9.8 feet), then mark a line on the ground.
5. Now back up your car (STRAIGHT) to almost 3 meters (9.8 feet) away from the wall. The center of the headlights (the "dot") needs to be at the 3 meter (9.8 feet) mark (diagram courtesy/copyright of Mazda).
6. Verify that the marks you made of the center of the headlights are accurate by measuring the distances from the center of the car mark you had made in step 2 using the measurements in the diagram shown below (courtesy/copyright of Mazda). Make corrections of those headlight center marks, as necessary.
7. Now, measure 3cm (1.2 inches) down from those center of headlights marks, then mark this spot well horizontally and vertically as a crosspoint. Your goal is now to aim to what is shown in the diagram below (courtesy/copyright of Mazda), using a Philips or JIS cross point screwdriver. If you start with horizontal aiming, you will then see how the DOT VOR aiming results in a very low aim after you have horizontally aimed your headlights. You will now realize that aiming the left side of the cut off line will result in the right side cut off line to go above the headlight center. This results in the greater lighting distance without adding glare to oncoming traffic.
You can find the adjusters as shown (diagram courtesy/copyright of Mazda):
Tip: Popping off the washer fluid bottle neck from the holder bracket gives enough room to fit your screwdriver through to the vertical adjuster.
8. Aiming is now complete. Turn AFS back on, if equipped and if desired.

Alternatively, you can aim your headlights using greater distance at 25 feet with a 3 inch downward aim from the headlight center point. The official Mazda instructions calls for using the 3 meter method. Either way works as 1.0% declination aim is achieved.

Now, enjoy your converted headlights. You can now enjoy these benefits:

Greater illumination distance (more "throw")

Less glare to oncoming drivers

Improved roadside signs, pedestrians, animals, etc. illumination

Do be aware of the disadvantages, as explained earlier:

You might blind people's mirrors as you pass them

Overhead road signs are not as greatly illuminated

Footnote: I confirmed the EDM 3rd gen has the same Z-beam pattern HID headlights, hence I became interested in "converting" my headlights over to reduce glare to oncoming traffic. After receiving shop manual information from across the pond, I became aware that not only would I reduce glare, I would also IMPROVE lighting performance! The diagrams posted (except for the 1st one) came from the European/rest of world shop manual. Only the 1st diagram came from the North American shop manual. I will report more of the results later, after some on road observations.

Update:
The lighting performance immensely improved over what was already good... the headlights can put down about 400 feet while glare to oncoming traffic is still tightly controlled to about 120 feet lighting distance... the curb side is lit very well as are road side signs... one thing is for sure, the headlights shine right into other car's driver side mirrors!

I haven't tried high beams yet on a dark road, but I can tell that they now light up like a freight train! I bet they can do 700 feet ahead!

This mod was well worth the effort!

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